| Products > Test Equipment |
| Keysight's new 34465A (6.5 digit) and 34470A (7.5 digit) bench multimeters |
| << < (132/145) > >> |
| TiN:
I would expect it to be just constant value stored in meter (typed in by calibration procedure step?) during the calibration, for user's convenience. Sure manual should cover this detail with correct explanation. I don't have / never played with 34461A/65A/70A to know shenanigans related to these meters, sorry. |
| dmm2018:
--- Quote from: TiN on January 03, 2019, 01:02:25 pm ---I would expect it to be just constant value stored in meter (typed in by calibration procedure step?) during the calibration, for user's convenience. Sure manual should cover this detail with correct explanation. I don't have / never played with 34461A/65A/70A to know shenanigans related to these meters, sorry. --- End quote --- I switched off the room's aircond and after nearly 10 mins the temperature shown on calibration menu changed from 24.2 to 25.2 degC. The new statistical data (after switching off aircond) is shown below. |
| dmm2018:
The temperature (shown on the calibration menu) which I referred to in my previous posts was taken from the menu in image below (copied from manual pp. 148). The temperature is not fixed but changing. After switching off the room aircond for one hour plus, the temperature is 27 degC now. The latest statistical data recorded in given below, now it's approaching 000.00003... |
| Dr. Frank:
--- Quote from: dmm2018 on January 03, 2019, 12:04:30 pm ---Hello... Received my 34470A one month plus ago but only started to use it 1~2 week ago. I have just done a test. A Fluke 884X Short was installed on the front panel terminals. The meter has been powered up nearly 90 mins before the statistical data recording (image below) was initiated. The calibration menu shows that the meter was calibrated in July 2018. Is the reading is OK? Since "Auto Zero" is ON, I thought the reading should be (very close) to 000.00000. Note: When the test was carried out, the (4m x 4m) room's aircond temperature setting was set to 18 degC, while the temperature shown on the calibration menu (besides Uptime) is around 24.1 degC. --- End quote --- Hello and Welcome to the forum! At first, this deep cooling in buildings in Malaysia and also in Singapore is always a torture for non - residents (like me), but also for analogue precision instruments and metrology processes. ;D The calibration process is done at about 23°C, even @ Keysight in Malaysia, where your instrument might have been calibrated (see your cal certificate). Highest uncertainty is achieved only at this calibration temperature. Otherwise, correction calculations using T.C.s apply. If you have a look into the manual, chapter about calibration, first thing calibrated are the offsets of all modes, especially DCV, DCI, Ohm. They use a low e.m.f., low ohm short to mitigate thermal voltages at the input jacks, but this calibration involves all (solder) junctions inside the instrument as well. See also this lengthy thread somewhere here, about DIY shorts. e.m.f. voltages of several µV can occur all the time, even at 'normal' lab temperatures, e.g. by using lab grade cables, but that can be mitigated by using the NULL function, before making the real measurement. That does not affect the calibration of the instrument, but increases the precision of the measurements. The gain constants (Full Scale) are also calibrated at ~23°C, and might out of specification, if you use the instrument @ these usual Malaysian temperatures. Even the '470A has a T.C. specification including its internal LTZ1000A reference, of about 2ppm/°C... 18°C room temperature is just at the edge of the usual lab temperature, maybe additional 10 ppm gain error. The 34465/470 have an ACAL function, which reduces this gain error at other temperatures to some amount (see manual), but it can't correct for these internal e.m.f. errors.. again that's what the NULL function is for.. In summary, these offsets you see @ 18°C are perfectly fine, and no sign of defect or mis-calibration. I suggest to prepare a special lab room at 23 +/- 2 °C. Frank |
| bson:
Somewhat tangential, but I often wish I could null my 34465A to the statistical average of a run, rather than take a new measurement. |
| Navigation |
| Message Index |
| Next page |
| Previous page |